This invention relates to hypodermic syringe and needle combinations. More particularly, it relates to a hypodermic syringe and needle combination wherein the needle can be permanently retracted into the syringe barrel.
Health care workers, such as nurses, and even housekeeping personnel are becoming more fearful of exposure to infectious diseases, such as hepatitis, AIDS, and the like through transmission by the accidental impalation with used hypodermic needles.
It has, therefore, become desirable to provide syringe and needle combinations which will reduce the possibility of such accidents.
Used needle and syringe combinations have also been implicated in drug abuse situations.
It is, therefore, also desirable to provide such combinations which may not easily be reused for such purposes.
Disposable hypodermic needle and syringe combinations, however, must be inexpensive to produce and easy to operate if they are to be widely utilized.
U.S. Pat. No. 4,592,744 describes such a combination wherein:
a standard syringe and needle are mounted in a clear plastic sheath. The needle extends through a hole in the bottom of the sheath. The end of the needle is covered with a cap. To use, the cap is removed and the standard medical procedures are carried out in the usual way but with the syringe still inside of the clear plastic sheath. After use, the syringe and needle are drawn back into the sheath and the needle is completely within the confines of the plastic sheath. Flanges within the sheath catch behind the lip of the needle as the syringe is withdrawn, trapping the needle within the sheath. The needle is thus unable to protrude at either end. (Column 2 lines 16 to 28)
The above system suffers from the fact that it requires a separate sheath to contain the used needle. The cost of the combination, which can be reused is, therefore, increased by the requirement for the separate sheath.
Furthermore, if an abuser were to wish to reuse the needle and syringe it would only be necessary to cut away the sheath and re-attach the needle to the syringe.
U.S. Pat. No. 4,702,738 discloses a disposable needle and syringe combination comprising a retractable sheath to cover the needle, after use, and lock in place thereby preventing accidental pricking by the exposed needle or reuse for drug abuse.
This system also suffers from the disadvantages noted above. Thus, if an abuser were to wish to reuse the combination for drug abuse, it would only be necessary to cut through the sheath thereby exposing the needle for reuse.
U.S. Pat. No. 4,747,829 discloses a "Prefilled syringe . . . " which suffers from the fact that it can only be used in "pre-filled" condition thus limiting its value. One would be required to have a large number of syringes if one would have many compositions to dispense. Furthermore, one could not use this syringe to withdraw fluids from a source such as a patient.
In addition, the preferred embodiment depends upon a pre-stressed needle which bows out of alignment with the plunger upon withdrawal from the barrel stem. This, of course, creates difficulties in positioning the needle within the syringe.
In U.S. Pat. No. 4,747,830 there is disclosed a retractable needle syringe wherein the needle is prevented from re-extension through the barrel stem, after being withdrawn. The Patent includes cooperating latching means, in the upper portions of the barrel inner wall and the outer wall of the plunger, which lock the needle assembly in an elevated position. The latching means are complex and would require expensive tooling.
The Patent also discloses means, (see e.g., FIG. 15), in the plunger head to engage the needle assembly for removal from the barrel stem. The engagement means 134 would have to break through a wall of a resilient flexible piston 136, which would require considerable force, before it would engage the needle assembly. Furthermore, at the time it would be necessary to break through the wall, said wall would be entrapped between the engaging means of the plunger and needle assembly thereby increasing the difficulty of breaking through it.
U.S. Pat. No. 4,770,655 describes a retractable needle syringe wherein the needle is canted relative to the longitudinal axis, within the barrel, after its use has been completed. In the disclosure the pin head at the proximal end of the needle, which is press-fitted into the exit stem of the barrel, is grasped by a flexible cavity at the distal end of the plunger. The cavity has a steplike structure of differing lengths and orientation which will cause the needle engaged therewith to cant relative to the longitudinal axis of the barrel.
The above invention suffers, inter alia, from the disadvantages of having a needle which is press-fitted into the barrel stem. That can result in the needle being pushed back into the barrel when an attempt is made to insert it into a receptacle for injection withdrawal. In addition, gripping of the narrow and thin pinhead of the needle and subsequent drawing of same into the stepped cavity of the plunger head would be difficult to achieve. The complex structure of the plunger head would also increase the costs of manufacturing the syringes.
U.S Pat. No. 4,955,869 discloses a retractable needle syringe comprising spring means at the distal end of the plunger causing the needle assembly thereof to be canted relative to the longitudinal axis of the barrel when said needle assembly has been retracted thereinto. The spring means comprises a compressible wedge-shaped seal at the distal end of the plunger. The wedge-shaped seal compresses upon engagement of the needle by an engaging means when said needle assembly is engaged by the barrel stem.
Among the disadvantages, is that the compressible spring means must comprise a material different from the plunger head. As a consequence, the plunger and spring means cannot be fabricated in a single step and the cost of manufacturing the syringe is increased.
It has now been found that the disadvantages of the prior art may be avoided by use of the needle and syringe combination of the present invention.